Fuse for an explosive projectile



K. E. W. HJELM FUSE FOR AN EXPLOSIVE PROJECTILE 2 Sheets-Sheet 1 FiledSept. 15, 1954 FIG.

INVENTOR.

KARL ERIK MLDEMAR HJELM FIG- 2 A1- TORNE? m 8 2 J Y H m M H W K E WHJELM FUSE FOR AN EXPLOSIVE PROJECTILE H Q m 2,836,118 Patented May 27,1958 FUSE FOR AN EXPLOSIVE PRGJECTILE Karl Erik Waldemar Hjelm, Bofors,Sweden, assignor to Aktiebolaget Bofors, Bofers, Sweden, a Swedishcorporation Application September 13, 1954, Serial No. 455,627

Claims priority, application Sweden September 25, 1953 7 Claims. Cl.102-71 The present invention relates to self-arming, striker operatedfuses for explosive projectiles, more particularly to self-arming,striker operated fuses which are selfdetonating a predetermined periodof time after having become armed.

One of the objects of the present invention is to provide a novel andimproved fuse of the general type above referred to, which is reliableand accurate in operation and simpler in design than fuses of the saidtype as heretofore known.

Another object of the invention is to provide a novel and improved fuseof the general type above referred to which, in response to the force ofinertia acting upon the projectile upon which the fuse is mounted,automatically becomes armed and initiates a timing means which in turncauses detonation of the fuse if the same is not detonated by actuationof the striker during the period of time for'which the timing means isset.

Other objects, features and advantages of the invention will be pointedout hereinafter and set forth in the appended claims forming part of theapplication.

In the accompanying drawing a preferred embodiment of the invention isshown by way of illustration and not by way of limitation.

In the drawings:

Fig. 1 is an isometric view of a fuse according to the invention in itssafety position.

Fig. 2 is a fragmentary isometric view of the timing means of the fuse.

Fig. 3 is an isometric view similar to Fig. l but showing the fuse inits armed position, and

Fig. 4 is an isometric view similar to Figs. 1 and 3 but showing thecomponents of the fuse in the positions ready for self-detonation of thefuse.

Referring to the figures in detail, the fuse mechanism is housed in aconventional casing or housing formed by a cylindrical part 1 and aconical part 2. The fuse mechanism comprises control slides 3 and 4axially displaceable, for instance in bores provided for this purpose inhousing part 1. Each slide has rack teeth 5 and 6 respectively whichconstitute part of the timing means more clearly f shown in Fig. 2. Thetiming means comprise gear shaft 7 in mesh with rack 5. Shaft 7 seats agear 9 in mesh with a gear 11' on a shaft 1' This shaft supports onecomponent 13 of a suitable step-by-step device, the other component 14of which is pivoted to housing part 1 by means of a pivot pin 15. Thestep-by-step device is exemplified by the ratchet or escape wheel 13coacting with the pawl 14. Gear shaft 7 is engaged by a gear 16 seatedupon a shaft 17 also supporting a gear 13. This gear is in engagementwith a gear 10 seated upon a gear shaft 8 in mesh with rack teeth 5 ofslide A spring 19 disposed in alignment with slide 4 urges, when loaded,slide 4 toward the nose of the fuse under the control of the timingmeans. For this purpose, one end of spring 19 is anchored within housingpart 1 and the other end abuts against slide 4.

The fuse mechanism further comprises a slide 21 which a is transverselyslidableyfor instance in a bore provided for this purpose in housingpart 1. The length of this transverse bore is such that slide 21 maymove from the position shown in Fig. l in heavy lines into the positionshown in 'thin lines. A spring 22 urges slide 21 into the latterposition. The slide has a transverse here or recess which is filled witha suitable ignition charge 23. Accordingly, slide 21 is sometimeshereinafter referred to as detonator slide. in the position of Fig. 1retains slide 21 in the heavy line position whereas in the position ofFig. 3, slide 3 permits movement of slide 21 into the thin line positionof Fig. l by the action of spring 22.

The fuse mechanism also comprises a striker pin 24 which is mountedaxially movable in housing part 1. The end of the striker facingde'tonator slide 21 is preferably pointed 111325 and formed with acollar 26. The opposite end of striker pin 24 mounts a disc 27 whichserves as a plunger axially displaceable in a sleeve 28. A spring 29fitted in sleeve 28 biases the striker pin into a position in whichpoint 25 is spaced apart from detonator slide 21.

As appears from the previous description, in the position of slide 21 asshown in Fig. l, the charge 23 is out of alignment with striker point 25whereas in the slide position according to Fig. 3, it is in alignmentwith the striker point. Accordingly, the position of Fig. l is thesafety position and the positionof Fig. 3 the armed position of slide21.

The fuse mechanism finally comprises a two-arm lever 30 pivotallymounted within housingpart 1. One arm of the lever coacts with collar 26of striker pin 24 for the purpose of actuating the striker as will bemore fully explained hereinafter. The other arm of lever 30 may coactwith the respective end of slide 4 which for this purpose is preferably.provided with a slanted head 4. A pin 31 serves to limit the axialmovement of slide 3 toward the nose of the fuse.

The operation of a fuse as hereinbefore described, is as follows:

Let it first be assumed that all the parts of the fuse mechanism are inthe positions of Fig. 1. According to this figure, slide 3 occupies itsuppermost position, that is, a position closest to the nose of the fuse.Slide 3 abuts against limit pin 31. As a result, the respective end ofdetonator slide 21 abuts against slide 3 so that the detonator slide islocked or retained in its safety position. Slide 4 is shown in anintermediate position below the detonator slideZl.

If, through an impact or any other cause, a downward movement beimparted to striker 24 against the action of spring 29, striker point 25will strike a wall portion of detonator slide 21 so that the fuse cannotbe accidentally detonate-d.

Let it now be assumed that the fuse is mounted on a projectile fired andin flight. As a result, the force of inertia acting upon slides 3 and 4will cause the same both to move backwardly relative to the nose of thefuse. The rate of the rearward movement of slides 3 and 4 relative tothe fuse housing and to each other is controlled by the ratio oftransmission of the gear train included in the timing means and theaction of the pawl and ratchet arrangement of the timing means. Whenslide 3 reaches the position of Fig. 3, detonator slide 21 is releasedand, hence, will be moved by the action of spring 22 into the positionof Fig. 3 in which the fuse is armed. in or near this position of slide3, gear shaft 7 becomes disengaged from rack teeth 5, or in other Words,slide 3 is disconnected from the timing means. The rearward movement ofslide 4 compresses spring 19 as is shown in Fig. 3. When theacceleration of the projectile has decreased to an extent such that thetension of spring 19 can overcome the force of inertia whichcorrespondingly decreases,

The slide coacts with slide 3 which fore slide head 4 makes contact withlever 30, the pro- .jectile strikes a target the fuse is detonated bythe resultant actuation of striker 24. However, if the striker is notactuated during the interval of time required for slide head 4' to movefrom the position of Fig. 3 into the position of Fig. 4, the slide headwill force lever 30 into the position of Fig. 4 thereby actuating thestriker and hence detonating the fuse. As is apparent from the previousdescription, the action of slide 4 assures that the fuse is detonated atthe end of a predetermined period of time after it has become armedthereby effectively preventing that an armed projectile falls back uponthe ground.

The detonation of the explosive charge of the projectile initiated bythe ignition or detonation of charge 23 is effected in a conventionalmanner'and a detailed description thereof is not essential for theunderstanding of the invention. It suffices to state that the ignitionof the charge in the detonator slide initiates a chain reaction causingthe explosion of the charge of the projectile which is also not shown.

While the invention has been described in detail with respect to acertain now preferred example and embodiment of the invention it will beunderstood by those skilled in the art after understanding theinvention, that various changes and modifications may be made withoutdeparting from the spirit and scope of the invention, and it isintended, therefore, to cover all such changes and modifications in theappended claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A striker operated and time controlled fuse for an explosiveprojectile comprising, in combination, a fuse housing, a movablestriker, a charge containing detonator slide coacting with the strikerfor setting off said charge by the striker and movable between a safetyposition and 'ly displaceable transversely thereto, the'force of inertiaacting upon a fuse mounted on a projectile in flight eifecting an axialdisplacement of said first and second control slides in one direction,the axial displacement of said first control slide causing movement ofthe same into the second position releasing the detonator slide, strikeractuating means engageable and movable by said second control slide,axial movement of the second control slide in the direction opposite tothe aforesaid one direction operating said striker actuating means,means biasing the second control slide towards said opposite directionfor operating the striker actuating means, and timing means controllingthe rate of axial movement of the second control slide into saidopposite direction whereby the striker is actuated a predeterminedperiod of time after movement of said detonator slide into its armedposition and the first control slide into said second position.

2. A fuse according to claim 1, wherein the said striker actuating meanscomprise lever means pivotally mounted in coacting relationship with thestriker and the second control slide, movement of said second controlslide into 'said opposite direction effecting engagement of said secondcontrol slide with said lever means to pivot said lever means into anactuating engagement with said striker.

3. A fuse according to claim 1, wherein the said biasing means comprisecompression spring means fixed at one end and engaged at the oppositeend by said second control slide, said spring means being adapted to becompressed by movement of said second control slide into the directioncaused by the force of inertia.

t, A striker operated and'time controlled fuse for an explosiveprojectile comprising, in combination, a moveable striker, a chargecontaining detonator slide coating with the striker for setting offth'echarge of the striker and movable between a safety position and anarmed position, a first control slide movable between a first positionretaining the detonator slide in the safety position thereof and asecond position releasing the said detonator slide for movement into thearmed position, a second moveable control slide, the said first andsecond control slides being disposed for movement in one direction bythe force of inertia acting upon a fuse mounted on a projectile inflight, the inertia movement of the first control slide effectingmovement thereof into the position releasing the detonator slide,striker actuating means engageable and operable by a movement of thesecond slide in a direction opposite to the aforesaid direction, timingmeans coupled with said control slides and controlling the rate ofmovement thereof, release means releasing the first control slide fromthe timing means upon movement of the said slide into the positionreleasing the detonator slide, and means biasing the second controlslide towards said opposite direction under the control of said timingmeans for operating said striker actuating means whereby the striker isactuated for setting ofiE said'detonator slide charge a predeterminedperiod of time after movement of said detonator slide into its armedposition. r a

5. A fuse according to claim 4, wherein said timing means comprise aspeed limiting means and a step-bystep motion transmitting meanscoupling the control slides with said speed limiting means, and whereinthe said release means'cornprise means disengaging said mo tiontransmitting means from the first control slide, in response to movementof 'said first control slide'to a predetermined position. 7

6. A fuse occording to claim 5, wherein said speech limiting meanscomprise a ratchet and pawl arrangement and said motion transmittingmeans comprises a gear train and rack gear teeth on each of said controlslides in meshing engagement with said gear train, and said releasemeans including a portion devoid of gear teeth immediately adjacent tothe rack gear teeth of the first control slide.

7. A fuse according to claim 6, wherein release of the first controlslide from the timing means is operative to free the second controlslide for the aforesaid actuation by said biasing means.

References Cited in the file of this patent UNITED STATES PATENTS1,943,706 Varaud Jan. 16, 1934 2,685,253 Apotheloz Aug. 3, 1954 FOREIGNPATENTS 396,171 Great Britain Aug. 3, 1933

